As an image display apparatus, for example, a liquid crystal display which displays an image by adjusting transmitted light using a liquid crystal composite or a plasma display which displays an image utilizing light emission generated by an electrical discharge is known as well as a projector which displays an image by projection. Such an image display apparatus carries out various kinds of image processing on an input image that is inputted from outside, and displays the image-processed image as an output image. The input image inputted to the image display apparatus from outside may be, for example, an input image based on a reproduced signal from a recording medium such as a DVD (digital versatile disk), an input image based on a broadcast signal from a broadcasting station, an input image based on a communication signal in data communication or the like.
The image processing carried out in the image display apparatus includes, for example, image enlargement processing (up-scaling and up-conversion), sharpness processing (sharpening) and the like are known. The image enlargement processing is to interpolate pixels and thus enlarge an image in order to display the image in an enlarged form. The sharpness processing is to uniformly enhance high-frequency components of the spatial frequency in an entire image area in order to sharpen a blurred and unsharp image.
Recently, in order to improve further the image quality of an image displayed by the image display apparatus, it is proposed that image processing (so-called “super-resolution processing”) to detect and selectively sharpen a contour part that is blurred before or after the enlargement of an image enlarged by interpolation of pixels should be applied to the image display apparatus. Japanese Patent Publication No. 2000-339450 and No. 8-336046 disclose examples of super-resolution processing.
However, traditionally, in carrying out in the image display apparatus the sharpness processing and the super-resolution processing, which are similar in terms of sharpening an image, proper combination of these two kinds of image processing is not thoroughly examined.